1. Field of the Invention
The present invention relates to a disk drive including an optical pickup for playing an optical disk and an optical pickup for writing or reading information signals to or from the optical disk.
This application claims the priority of the Japanese Patent Application No. 2003-347673 filed on Oct. 6, 2003, the entirety of which is incorporated by reference herein.
2. Description of the Related Art
There has been proposed an optical disk drive including two optical pickups, one of which is to play a CD (compact disk), CD-R, CD-ROM or the like and the other of which is to play a DVD (digital versatile disk) (cf. the Japanese Patent Application Laid Open Nos. H09-282671 and H09-282672). The disk drive includes a device body and a sub chassis disposed inside the device body, and has disposed on the sub chassis a disk rotation drive to rotate each of various types of disk-shaped recording media while holding it, first pickup unit to read information signals or the like from a DVD, second pickup unit to play a CD, CD-R or CD-ROM and a skew adjusting mechanism to adjust an inclination of the first and second pickup units.
The sub chassis is formed generally rectangular, and has a damping member formed from rubber or the like provided near each corner thereof. The sub chassis is disposed inside the device body with the damping members laid between them, and thus it is isolated from vibration. Also, on the sub chassis, there are provided the disk rotation drive disposed nearly at the center, and the first and second pickup units disposed opposite to each other across the disk rotation drive or at a predetermined angle defined between them.
The disk rotation drive to hold each of various types of disk-shaped recording media rotatably includes a disk table on which the disk-shaped recording medium is place, and a spindle motor with a spindle shaft to which the disk table is fixed. The disk rotation drive rotates the disk-shaped recording medium set on the disk table at a constant linear velocity or angular velocity. The disk rotation drive is disposed nearly at the center of the sub chassis.
The first pickup unit to play a DVD is supported on a pair of guide shafts provided in parallel to the length of the sub chassis, and can freely be moved by a pickup moving mechanism radially of the DVD. Also, the first pickup unit includes a pickup having a semiconductor laser that emits a laser beam of 650 or 635 nm in wavelength, and a skew sensor.
The second pickup unit to play a CD, CD-R or CD-ROM is supported on the pair of guide shafts provided in parallel to the length of the sub chassis, and can freely be moved by a pickup moving mechanism radially of a CD or the like. Also, the second pickup unit includes a pickup having a semiconductor laser that emits a laser beam of 780 nm in wavelength.
In the disk drive, when a disk-shaped recording medium is held on the disk table, its type is detected and either the first or second pickup unit is selected which is suitable for the specifications of the recording medium. Then, the first or second pickup unit selected correspondingly to the type of the disk-shaped recording medium set on the disk table is activated to emit a laser beam having a predetermined wavelength for reading information signals from the recording medium. Also, an inclination of the reading laser beam is detected by the skew sensor provided on the first pickup unit with reference to a skew detection hole, and one of the guide shafts in pair is driven by the skew adjusting mechanism. Thus, each pickup in the first or second pickup unit supported on the pair of guide shafts has the inclination of an objective lens thereof adjusted for adjustment of a skew.
In such a disk drive, the pair of guide shafts is provided to extend over the sub chassis and the first and second pickup units supported on the pair of guide shafts are disposed on the same sub chassis, so that the first and second pickup units can have the height thereof defined accurately. Therefore, the disk drive can accurately position the disk-shaped recording medium without any troublesome positional adjustment of the first and second pickup units in relation to the disk-shaped recording medium.
In the above disk drive, however, either the first or second optical pickup unit is selected correspondingly to the type of a disk-shaped recording medium inserted in the device body, the pickup in the selected one of the optical pickup units is moved radially of the disk-shaped recording medium. At this time, the pickup in the other optical pickup unit not selected is positioned at the inner or outer radius of the disk-shaped recording medium. Therefore, if the pickup in the selected optical pickup unit moves to the outer or inner radius of the disk-shaped recording medium, the weight of the sub chassis will be imbalanced.
More specifically, the disk drive has the disk rotation drive provided generally at the center of the sub chassis and the first and second pickup units provided in positions opposite to each other across the disk rotation drive so that when each of the pickups in the first and second pickup units is in an initial position at the outer or inner radius of a disk-shaped recording medium, the center of gravity of the sub chassis will come to the disk rotation drive including the spindle motor which will be a source of vibration. However, when one of the optical pickup units, selected correspondingly to the type of a disk-shaped recording medium set in place, is moved, the weight balance of the sub chassis will be lost.
Thus, the center of gravity of the sub chassis will be off the spindle motor which is the source of vibration, vibration isolation will be lost, disk-shaped recording medium cannot be rotated stably, and no skew can be detected accurately.
Also, there have recently been prevailing disk drives capable of reading information signals from a disk-shaped recording medium such as a DVD and also writing information signals to the recording medium. Such a disk drive is required to have a capability of detecting and correcting an inclination of the optical axis of a laser beam in relation to the disk-shaped recording medium in which the recording track pitch is small, such as a DVD, with a higher accuracy than that in a disk drive which plays a CD or the like.
Also, the distance between an optical disk and skew sensor always varies since it depends upon the type of a disk-shaped recording medium such as CD, DVD or the like, state in which the disk-shaped recording medium is chucked to the disk table, warp of the disk-shaped recording medium and so forth. On this account, skew detection and adjustment are always done while the disk-shaped recording medium is being rotated, for an accurate skew detection of the skew sensor.
In the aforementioned disk drive, however, a pair of guide shafts is provided to extend on one sub chassis, a first pickup unit dedicated for CD and second pickup unit dedicated for DVD are supported on the guide shafts, respectively, and skew of these first and second pickup units is adjusted through adjustment of an inclination of the guide shaft. Thus, it is difficult to make an accurate, real-time skew adjustment while the disk-shaped recording medium is being rotated.
Also, there have recently been prevailing disk drives capable of reading information signals from a disk-shaped recording medium such as a DVD and also writing information signals to the recording medium. Such a disk drive is required to have a capability of accurately detecting the type of a disk-shaped recording medium set in place in order to define a write or read format, and writing or reading information signals to or from the disk-shaped recording medium in a format corresponding to the detected type of the disk-shaped recording medium.
Also, there have recently been prevailing disk drives capable of reading information signals from a disk-shaped recording medium such as a DVD and also writing information signals to the recording medium. Such a disk drive is designed to write or read information signals to or from a disk-shaped recording medium whose recording track pitch is small, such as a DVD, by having a laser beam in a predetermined format corresponding to the type of the inserted disk-shaped recording medium track a recording track on the latter while accurately controlling tracking and focusing in relation to the disk-shaped recording medium.
Conventionally, to verify whether information signals have normally been written to such a high recording-density disk-shaped recording medium, an optical pickup unit used for writing information signals is used to read information signals. Therefore, since the information signals are read after writing the information signals, the verification cannot be done rapidly.
Also, in the conventional disk drive, since a disk-shaped recording medium is to be carried along the length of a sub chassis, so it has to be carried over a long distance from a disk slot in a device body to a disk table. Also, the disk transport mechanism to carry a disk-shaped recording medium along the length of the sub chassis is considerably large. Further, because of the long carrying distance, it will take a considerably long time to inset or eject the disk-shaped recording medium.
Also, in case the disk-shaped recording medium is to be carried on a disk tray, the disk tray should have formed therein openings through which first and second optical pickup units can be exposed to the signal recording surface of the disk recording medium within a range between the inner and outer radii of the latter. The openings have to be formed opposite to each other across the center of a disk mount. Therefore, the rigidity of the disk tray cannot be assured and also the disk tray should be produced by a complicated process.
Also, in the conventional disk drive, a damping member to isolate a sub chassis from vibration is provided near each corner of the sub chassis, and a spindle motor as a source of vibration is disposed nearly at the center of the sub chassis. Therefore, the damping member is so separated from the source of vibration that it cannot effectively absorb vibration from the spindle motor. Also, the damping member is provided near each corner of the sub chassis. As the first or second optical pickup unit is moved to the inner radius of a disk-shaped recording medium and thus approaches the spindle motor as the source of vibration, the damping member will be separated from the first or second optical pickup unit. Thus, write or read of information signals will possibly be adversely affected by the vibration of the spindle motor.